1. Field of the Invention
The present invention relates to a billing system and method for charging users for the utilization of a finite amount of a shared resource. The present invention is particularly suitable for charging computer resource users.
2. Description of the Related Art
Japanese Patent No. 3,322,241 discloses a billing system for a mobile communication network for charging users according to average utilization rates of wireless base stations. A billing rank is determined for each base station in advance, based on its average utilization rate. Users are charged according to both the billing rank and the amount of traffic of their base station. For each base station, a ranking-based billing scheme is established so that users are charged with a low discount rate when the utilization rate of the base station is high. Likewise, a traffic-based billing scheme is established so that the discount rate is low when the congestion level of the traffic is high.
A billing system for a mobile communication network is also disclosed in Japanese Patent Publication 2002-368782. According to this billing system, different discount rates are offered during high congestion periods depending on applications (such as FTP, TELNET and HTTP) and congestion levels of traffic. Each base station classifies received packets into groups according to users and application protocols and counts the received packets according to the groups. A base station controller transmits a measurement packet to the base station once a certain number of packets the base station receives. In response to the measurement packet, the base station determines the time interval between two measurement packets and calculates the congestion level of traffic from the determined time interval. If the calculated congestion level exceeds a predetermined threshold, the base station recognizes that a delay has occurred in packet transmission. Billing data is transmitted from the base station to a server either once when the user terminates communication or periodically during communication.
According to a billing system disclosed in Japanese Patent Publication 2004-200891 for a fixed communications network, users are charged an extra fee if their communication routes are using a switching equipment of which the utilization rate exceeds an upper limit.
However, a first problem that is common to the prior art techniques is the difficulty for administrators or owners of resources in estimating the total income (i.e., charge) obtained from the users of the resources (such as base stations, applications and communication links). This problem arises from the nonexistence of criteria to determine discount rates.
A second problem is that the prior art techniques need a large storage space for billing because of the necessity to maintain as a table for example, the ranks of base stations, discount rates for congestion, or surcharges for overloaded switching equipments.